1. Field of the Invention
The present invention relates to a method for manufacturing beer. More particularly, the present invention relates to a beer manufacturing process in which self-liquefying barley starch granules containing a high content of d-amylase enzyme are used alone or are mixed with a starch adjunct such as wheat, corn or rice starch in the preparation of the mixture to be fermented for the manufacture of beer.
2. Description of the Prior Art
Starch is usually obtained in the form of granules by separation from starch containing plants or plant parts. In the brewing of beer, the starch is first pasted and then liquefied by cleavage of the starch molecules to reduce the viscosity of the starch paste. The granules are initially insoluble in water, but when heated in water, they begin to swell, imbibing water rapidly until they are many times their original size. Upon continued heating, the granules begin to disintegrate and the viscosity of the water-starch mixture begins to rapidly increase until it reaches a maximum, thereby forming a paste. If the starch is a waxy starch, further heating after the maximum viscosity is reached results in an initial drop in viscosity, however, cooling of the partially solubilized paste causes the hydrated molecules and segments of granules to insolubilize forming a paste probably through H-bonding of starch chains. In the case of normal starches, this paste on cooling will form a stiff gel. Waxy starches will remain somewhat fluid. This initial cooking phase usually requires heating to temperatures in the range of 85.degree. - 105.degree. C, depending upon the particular variety of starch being treated. In this critical cooking phase, viscosities as low as 300-400 Brabender viscosity units are attainable, however, under miscroscopic examination, the granules will show a substantial increase in size resulting in a substantial reduction in size of the starch molecules.
In enzyme conversion, the enzymes rupture interior chains on both the amylase and amylopectin molecules resulting in a substantial reduction in size of the starch molecules. The smaller molecues are usually referred to as .alpha. dextrins. Liquefication is said to occur when 8% pastes show a Brabender viscosity in the range of 0-20 units. However, the exact extent of liquefication will be determined by the particular application for the starch.
In the past, where it has been desired to liquefy the paste in the brewing of beer, enzyme conversion to liquefy the paste was accomplished by addition of an enzyme into the paste followed by mild heating. Thus, in order to make a liquefied product suitable for beer brewing, a malt infusion was first prepared which contained a high percentage of .alpha.-amylase and the infusion was added to the starch paste.
In normal brewing operations, part of the barley malt is added to an adjunct (corn starch, rice, or corn grits) and the mixture heated to boiling. During the heating process, the starch is gelatinized and partially converted; however the enzyme is destroyed before the process is completed. The cooked adjunct is then added to the main malt mash which is heated to 65.degree., held for a half hour and then gradually heated to 75.degree. which it is maintained for 3-4 hours in order to convert and extract as much material as possible.
It is known that most cereal grains do not contain substantial amounts of .alpha.-amylase. Thus, in order to obtain a starch source containing sufficient amounts of .alpha.-amylase for the fermentation process, it has been necessary to allow a cereal grain, normally barley, to germinate. The germination process is only allowed to continue until the .alpha.-amylase content of the barley increases by a factor of 200 to 10,000. This process is known in the brewing art as malting. That is, the .alpha.-amylase content of the barley increases from 0.045 units before malting to 90.0 after malting.
Barley contains .beta.amylase. However .beta.amylase has very limited action on starch attacking only the non-reducing ends of the starch chains. It cannot attack interior chains so it has a very minimal effect on reducing viscosity of starch paste. Even when .alpha.-amylase is produced in cereals by malting it will not be retained on the starch granule since it is quite water soluble. Furthermore it is sensitive to heat and therefore is destroyed during the cooking phase.
It was long recognized that if the enzyme could be protected during these initial processing stages, that a self-liquefying starch could be obtined which would not require the addition of further enzymes to the starch paste. However, heretofore no satisfactory technique for protecting the enzymes has been developed. For instance, consideration was given to bind the enzymes by lime water treatment so that it is not steeped from the grains too quickly, or by formaldehyde treatment or the like. None of these techniques, however, have proven to be commercially acceptable or to protect a large enough percentage of the enzymes.
If a starch granule could be developed which would be self-liquefying without the addition of further enzymes, or, even more desirably, without cooking, the demand for such a starch source in the brewing industry would be quite significant. The starch source could be used as a replacement for corn syrup, and if the source were prepared from barley grain, it would have a substantially lower cost and, hence, would be quite competitive with corn syrup. Since it would enable the elimination of at least one and possible two processing steps normally required for the utilization of starch, it would be highly advantageous in a wide variety of applications.
A need therefore, continues to exist for a self-liquefying starch material for use as a starch source in the brewing of beer.